1261 has 4 divisors (see below), whose sum is σ = 1372.
Its totient is φ = 1152.
The previous prime is 1259. The next prime is 1277. The reversal of 1261 is 1621.
It is the 15-th star number.
It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.
It can be written as a sum of positive squares in 2 ways, for example, as 361 + 900 = 19^2 + 30^2
It is a 4-Lehmer number, since φ(1261) divides (1261-1)4.
It is a cyclic number.
It is not a de Polignac number, because 1261 - 21 = 1259 is a prime.
It is the 36-th Hogben number.
It is a Duffinian number.
1261 is a lucky number.
It is a plaindrome in base 8.
It is a nialpdrome in base 13 and base 14.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (1201) by changing a digit.
It is a nontrivial repunit in base 35.
It is a pernicious number, because its binary representation contains a prime number (7) of ones.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 36 + ... + 61.
It is an arithmetic number, because the mean of its divisors is an integer number (343).
21261 is an apocalyptic number.
1261 is the 21-st hex number.
It is an amenable number.
1261 is a deficient number, since it is larger than the sum of its proper divisors (111).
1261 is an equidigital number, since it uses as much as digits as its factorization.
1261 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 110.
The product of its digits is 12, while the sum is 10.
The square root of 1261 is about 35.5105618091.
The cubic root of 1261 is about 10.8036795875.
Adding to 1261 its reverse (1621), we get a palindrome (2882).
It can be divided in two parts, 1 and 261, that added together give a palindrome (262).
The spelling of 1261 in words is "one thousand, two hundred sixty-one".